The first prostheses had a merely esthetical function meaning that they were not functional. Thereafter, mechanical prostheses were developed. Still later, the upper limb (arm) prosthesis, which is operated by a whip that follows the movements of the shoulder, came to be substituted for the traditional mechanical clamp or hook prosthesis. Today there are functional prostheses with a higher technological development which allows them to be ergonomic, easily operated, and having better aesthetics, coming closer to the appearance and functioning of a real leg or arm.
Based on research, we have found several technologies which apply different mechanisms that focus on the field of the upper limb prostheses, particularly those for the hand. From these technologies, we shall list the ones having a closer technical resemblance to the functional mechanism for a functional prosthesis for a hand.
U.S. Pat. No. 5,013,326 (“U.S. '326 patent”) describes a hand provided with turned fingers of a certain curvature, their axis being at a 30° angle with respect to the angle of the forearm. This device is able to grab elements or lift small objects located on a surface. The movement of the turned phalanges is transmitted by means of an internal rack.
Japanese Patent 2,080,044 (“JP '044”) bases its operation on a mechanism which is very similar to the one described in the U.S. '326 patent. The mechanical system in JP '044 corresponds to 3 hooks located in such manner that they simulate the thumb, index and middle fingers. It approaches part of its description on the actuator that generates the movement of the hand.
Document WO 0069375, 1968 (“WO '375”) discloses a hand prosthesis which has an individual movement in each of its five fingers, each finger having an independent actuator whose movement is controlled by means of extensometric calipers.
U.S. Pat. No. 5,200,679, 1993 (“U.S. '679 patent”) describes a robotic hand which uses a prosthetics element which includes 5 fingers. It has a dual action motor that uses two cables to generate the opening and closing movements of the hand. When the motor turns in one direction, it generates tension on the first cable, which causes the phalanges to retract toward the palm of the hand, generating the closing movement. Afterwards, tension is generated on the second cable, due to the inverse turn of the motor, that causes the fingers to return to the original extension position which is the opening of the hand.
U.S. Pat. No. 4,114,464 (“U.S. '464”) deals with an artificial hand mechanism which has at least one finger and a thumb which generate together the opening and closing movement of the hand by means of a gear joined to each one of them. At the same time, they are adjusted to a screw tip gear that is coupled to a motor.
U.S. Pat. No. 4,377,305 (“the '305 patent”) describes the functioning of an artificial hand which has two fasteners which articulate on a bolt that provides them with the opening and closing movement of the fasteners, and also provides them with a flexion-extension movement over the same quadrant or plane as the opening and closing movement. The fasteners can rotate since they are assembled on an axis parallel to the axis of the bolt. The opening and closing movement of the fasteners is done by means of a curve section dual rack and a straight gear mechanically coupled to them. It also has an adduction and abduction movement as well as a wrist turn.
U.S. Pat. No. 5,080,681, 1990 (“U.S. '681”) describes the functioning of an artificial hand that consists of two mobile phalanges and a hook that simulates the thumb. The closing and opening movement of the phalanges described in this prosthetic mechanism is provided by means of a mobile mechanism activated by an actuator. When activated, the mobile device glides through a guide which is located on the chassis of the artificial hand. It has a system of artificial tendons which are joined to the mobile device on one side and then to the phalanges. When the device moves towards proximal (the patient's body), the tendons contract and generate the closing movement of the fingers and when the device moves towards distal, the tendons relax and generate the opening movement of the fingers.
U.S. Pat. No. 5,888,246 (“U.S. '246”) describes the coupling between a worm gear and a round gear joined to a finger member. The worm gear transmits the movement to the round gear which generates the angular movement of a member simulating a finger. This coupling may be coupled to an artificial hand.
U.S. Pat. No. 5,378,033 (“U.S. '033”) describes a complex hand mechanism which consists of three fingers assembled on a pair of plates which are toothed in three sections of their periphery. The hand may be turned by means of gears which transmit the movement coming from a motor. Opening and closing movements are given by means of a mechanism which has two conical gears joined, one to the axis of the motor and the other to a cam with a follower that is joined to three elements that serve as a guide for the base of the fingers. The maximum elevation trajectory of the follower generates a movement to the three guides joined to each finger. They, in turn, transmit the displacement movement to the base of the fingers that articulate in one of the disks, thus generating a lever effect with which they open. This movement is transmitted to the phalanges by means of a system of gears coupled from the base of the finger to the distal phalanx of the finger on both sides of the finger. When the follower moves upward, the fingers open; when the follower descends, the fingers close.
Document GB 2072020 (“GB '020”) describes the functioning of a hand prosthesis that uses a standard worm gear for the opening and closing action of the fingers. This particular hand prosthesis is similar to the invention except that the movement of the finger, the placement of the motor, the type of impeller screw, and the coupling of the motor to the worm gear are different in the present invention from those disclosed in GB '020.
Document CN 2680418Y (“CN '18Y”) describes the functioning of an artificial hand using the worm gear system aided by a lever or rod to move the thumb.
Among the disclosures described herein, and others existing in the field, there are some hand prostheses which control the function of fingers opening and closing using a worm gear with a standard chord. The present invention is an improvement over such other prostheses in that not only the drive system of the fingers of the present invention, but also the plate that supports the elements, provide a functionality of the fingers and hand that is not found in prior art embodiments.